Despite criticism that it will revisit yet more thorny tangles from Russia’s past, Parliament has passed a law to restore to religious organizations property seized by the state in Soviet times.

To leaders of the Russian Orthodox Church, the State Duma’s passage of the law last Friday was a major step toward justice. To critics, the law that was passed by 345 votes to 42 and is due to be signed by President Dmitri A. Medvedev, is a recipe for social unrest and a threat to cultural monuments.

Under the law, the federal, regional and municipal authorities have two years to hand over property after a decision is made on a claim by the church, either for rent-free use or in a full transfer of ownership. Previously, said Ksenia Chernega, a nun who is the Moscow Patriarchate’s legal counsel, restoration of church property, which started in the 1990s after the fall of Communism, was regulated only at the federal level.

While the law addresses religious property generally, it is seen as broadly favoring the Russian Orthodox Church, the largest religious organization in the nation, though all groups had property taken by the Communists.

Prime Minister Vladimir V. Putin had promised Patriarch Kirill, head of the Orthodox Church, in January “to return to religious organizations that which by rights belongs to them.”

On Saturday, in symbolic anticipation of reclaiming more property, the patriarch served a liturgy at the cathedral in Kronstadt, a naval base near St. Petersburg, that for decades housed a movie theater, an officers’ club and a naval museum and is now being restored under the patronage of Mr. Medvedev’s wife, Svetlana, who attended the service.

In his sermon, Patriarch Kirill praised the law and spoke of “great efforts” directed at thwarting it. “This means that the enemy of the human race is not abandoning hopes of erasing sacred symbols and great values from human remembrance,” he said.

But one observer, Vitaly Tretyakov, a political commentator, warned at a discussion of the law in Moscow last month: “I’m afraid of any redistribution in our country. As soon as redistribution begins, something bad always happens.”

Property in Russia has often changed hands by fiat, and never more so than after the 1917 Bolshevik Revolution, which saw the wholesale destruction or transfer to the state of Tsarist, aristocratic, merchant and peasant property.

Unlike other East European countries and the Baltic states, Russia did not offer restitution of property after the collapse of Communism.

The new law dictates that government bodies must post all property claims and decisions on Web sites. Claims can be disputed in court and legal challenges are expected. The concept of former church real estate extends not only to buildings that were used for worship, but also to church-run hospitals, schools and residential buildings.

In Soviet times, monasteries, if not destroyed, were often turned into residences. The new law stipulates that any people living on, and forced to leave, church property must get new housing.

Thousands of museums across the country are in former church-connected buildings. Indeed, churches that were not destroyed were often saved by being turned into museums or concert halls.

Solovki, for instance, the island monastery that became one of the first Gulag camps, was turned into a museum and nature preserve after Communism’s fall and is now being restored as a monastery. In other cases, church leaders support the renewed use of icons that have been in museums for decades, while the museums fear the icons will be spoiled.

In Kaliningrad, the former German Königsberg that ended up in Soviet hands after World War II, questions of church property are especially complex. The regional legislature voted this month to transfer more than a dozen former Catholic and Lutheran churches, cathedrals and Teutonic castles to the Russian Orthodox Church, which says Orthodox believers there are underserved. (Patriarch Kirill was Metropolitian of Smolensk and Kaliningrad before his enthronement.

Moscow’s relations with the Vatican had been improving, but Archbishop Paolo Pezzi, whose diocese oversees Moscow and Kaliningrad, said that the region’s legislators were “profoundly mistaken” in their effort to hand over the neo-Gothic Church of the Holy Family to the Russian Orthodox rather than the Roman Catholic Church. The church is now used by the Kaliningrad Philharmonic.

The debate has reached across borders. After protests from the government of neighboring Lithuania, the Kaliningrad region is reconsidering its decision to include in the transfer list a Lutheran church that is the burial site of Kristijonas Donelaitis, a Lithuanian pastor and poet.